Polycrystal silicon is suitably used as a raw material of semiconductors and solar cells which are further going to be developed and demanded in the days to come. In a process for producing polycrystal silicon, an apparatus for producing polycrystal silicon provided with a reacting furnace and a circulation type purification system is used. In the reacting furnace, polycrystal silicon is manufactured from a mixed gas of chlorosilanes and hydrogen. In the purification system, a hydrogen gas is extracted from an exhaust gas that has been generated in the reacting furnace and the hydrogen gas is reintroduced into the reacting furnace.
However, oligomers of silanes (SixHyClz) and a silicon powder that are obtained as a by-product in a process for producing polycrystal silicon adhere to a pipe whereby the pipe becomes blocked and the apparatus is damaged in a continuous operation of the apparatus for producing polycrystal silicon.
Under these circumstances, in the Patent documents 1 and 2, a filter made of activated carbon or the like is disposed on the upstream side of at least one unit that configures the above described purification system and an exhaust gas is made to pass through the filter.